Stephen Hawking’s final paper, just released, tackled the “information paradox”

Quantum theory specifies that information is never lost but what happens to the information when a black hole vanishes?

In the latest paper, Hawking (1942-2018) and his colleagues show how some information at least may be preserved. Toss an object into a black hole and the black hole’s temperature ought to change. So too will a property called entropy, a measure of an object’s internal disorder, which rises the hotter it gets.

The physicists, including Sasha Haco at Cambridge and Andrew Strominger at Harvard, show that a black hole’s entropy may be recorded by photons that surround the black hole’s event horizon, the point at which light cannot escape the intense gravitational pull. They call this sheen of photons “soft hair”.